Gang saw with improved damping means

ABSTRACT

A crankshaft cradle is provided to damp out vibrations in a gang saw. The cradle is used to support the crankshaft and is pivotally attached to the gang saw frame. Forces that would normally be transferred from the crankshaft to the frame are damped out by means of the movable cradle, the movable cradle being pivotally attached to the frame by pendulum links.

United States Patent Johansson July 29, 1975 GANG SAW WITH IMPROVEDDAMPING 2,740,436 4/1956 Woodruff 83/748 MEANS 3,763,716 10/1973Blomberg 74/604 3,791,227 2/1974 Cherry 74/52 [75] Inventor: TageHjalmar Johansson.

Sollentuna, Sweden [73] Assignee: Kockum Industri Aktiebolag,

Soderhamn, Sweden [22] Filed: Apr. 5, 1974 [21] Appl. No.: 458,358

[30] Foreign Application Priority Data Apr. 13, 1973 Germany 2318820[52] U.S. Cl. 83/748; 74/52; 74/604 [51] Int. Cl. B27B 3/12 [58] Fieldof Search 83/748. 751, 779; 74/604, 74/603, 44, 42, 52

[56] References Cited UNITED STATES PATENTS 834,958 11/1906 Wilkin83/748 Primary ExaminerDonald R. Schran Attorney, Agent, orFirm-Cushman, Darby & Cushman [57] ABSTRACT A crankshaft cradle isprovided to damp out vibrations in a gang saw. The cradle is used tosupport the crankshaft and is pivotally attached to the gang saw frame.Forces that would normally be transferred from the crankshaft to theframe are damped out by means of the movable cradle, the movable cradlebeing pivotally attached to the frame by pendulum links.

4 Claims, 4 Drawing Figures PATENTEI] JUL 2 9 I975 W F MM Fig. 4

GANG SAW WITH IMPROVED DAMPING MEANS BACKGROUND OF THE INVENTION Thisinvention relates to gang saws. and more particularly to a device to aidin damping vibrations in a gang saw frame.

Gang saws are often used for the conversion of saw logs into boards andplanks. The gang saws commonly used today have a main frame resting on afoundation wherein the frame has vertical guides for a sash in which thesash holds parallel vertical saw blades so that the blades may bereciprocated vertically in the main frame. In such a gang saw acrankshaft is typically coupled with the sash by means of a connectingrod.

The improvements made in recent years to gang saws of this kind relateto individual components, such as the saw blades, the sash and thebearings. The basic design, on the other hand, has not been changed andthe problems relating to the gang saw vibrations still exist with thepresent-day gang saws. Therefore, a careful anchor ing of the main frameto a foundation is required. The vibrations to a substantial extent arecaused by the strong fluctuating forces which are produced as aconsequence of the movements of the sash, the connecting rod and thecounterweight of the crankshaft and which are transmitted to the framethrough the crankshaft.

Swedish patent 198,133 discloses the use of a freely oscillating weighton the top of a frame structure in which the natural frequency of thependulum is adjusted to act in opposition to the vibrations of the mainframe. This device has been found to be inadequate when applied to atypical gang saw, because a gang saw is subjected to a wide variation ofvibrations, and a more responsive damping method is required.

Another Swedish patent No. 198,921, attempts to deal with the crankshaftto frame vibration problem by utilizing unbalanced weights connected tothe crankshaft and rotated in opposite directions at the speed of thecrankshaft to reduce vertical vibrations in the main frame. Suchunbalanced weights must be driven by a separate power source from thecrankshaft power source and are hence impractical.

The instant invention provides a solution to the vibration problem byemploying a novel crankshaft cradle structure.

The object of the invention is to provide a gang saw of the kindhereinafter described in which the vibrations to the main frame aresubstantially reduced.

To this end, in the gang saw according to the invention, the crankshaftis rotatably journaled in a cradle which is carried by the main frameand movable relative to the main frame substantially horizontally andtransversely of the axis of rotation of the crankshaft under theinfluence of the forces which the crankshaft imposes on the cradleduring the rotation of the crankshaft.

Since the crankshaft is thus free to move relative to the main framehorizontally and transversely of its axis, it will, during its rotation,reciprocate horizontally at the frequency of the vertical reciprocationof the sash. This horizontal reciprocation has a phase shift relative tothe vertical sash reciprocation such that the crankshaft is in its meanor center position when the sash is in its extreme positions and thecrankshaft is at its extreme horizontal positions when the sash is atits center or mean position. These movements of the crankshaft result ina very substantial reduction of the fluctuations of the forces imposedon the main frame by the crankshaft and, hence, a substantial reductionof the vibrations of the main frame.

The movability of the cradle may be realized in different ways. Forexample, the cradle may be slidably mounted on straight, horizontalguides extending transversely of the crankshaft and resiliently urgedtowards its center position by springs opposing the reciprocation.Instead of straight guides the gang saw may have guides which are curvedin the vertical direction such that the cradle is gradually raisedrelative to the main frame as it is displaced from the mean position onso that the reciprocation is opposed by the weight of the cradle and thecrankshaft.

In the preferred embodiment, however, the cradle is suspended inpendulum fashion from the main frame on both sides of the crankshaft bymeans of pendulum links. Preferably the pendulum links are parallel orapproximately parallel.

Additional objects of the present invention reside in the specificconstruction of the exemplary apparatus hereinafter particularlydescribed in the specification and shown in the several drawings.

BRIEF DESCRIPTION OF THE DRAWINGS A gang saw constructed in accordancewith the invention will be described hereinafter with reference to theaccompanying drawings.

FIG. 1 is a side elevational view of one embodiment of the gang sawaccording to the invention.

FIG. 2 shows the lower portion of the gang saw as taken along lines 22of FIG. 1.

FIG. 3 is a schematic drawing which illustrates the crankshaft movementin relation to an xy coordinate system.

FIG. 4 graphically illustrates the position of the sash along an xcoordinate with respect to the position of the crankshaft along a ycoordinate as the crankshaft is rotated through a phase angle, (b.

Novel features of the improved device in accordance with the presentinvention will be more readily understood from a consideration of thefollowing description taken together with the accompanying drawing, inwhich certain preferred adaptations are illustrated with the variousparts thereof identified by suitable reference characters in each of theviews, and in which:

DETAILED DESCRIPTION OF THE INVENTION The gang saw as illustrated inFIG. I has a main frame 11 secured to a foundation 12. An electric orhydraulic motor 13 rotates a crank mechanism, which includes acrankshaft 14 supported by the lower portion of the main frame and aconnecting rod 15. The crankshaft 14 is rotated at a constant speed. Theupper portion of the main frame 11 is provided with vertical sash guides16 and 16a which may be adjustable. These guides 16 and 16a coact withslide blocks 17 on a rigid sash 18 in which a plurality of parallel sawblades 19 are secured in vertical planes. The sash 18 is pivotallyconnected to the connecting rod 15 and thus moves up and down the mainfram 11 when the crankshaft 14 is rotated. The crankshaft is providedwith a counterweight (not shown) which is disposed diametricallyopposite to the crank pin and serves to balance the weight of the sashand the connecting rod. Logs to be sawed are moved horizontally throughthe main frame 11 and the sash 18 by means of upper and lower feed rolls20 in a manner well known. The feed rolls are adjustable in a verticalplane to accomodate logs of varying diamcters.

So far as it has been described above, the illustrated gang saw isconventional. The novel feature of this invention resides in the factthat the bearings 21 of the crankshaft 14 are not stationary in the mainframe 11 but are rather mounted on a cradle 22 which is suspended inpendulum fashion from the main frame I! on both sides of the crankshaft14 through four parallel links 23 of equal lengths. The cradle 22includes two transverse beams 24 rigidly connected to each other throughtwo longitudinal beams 25.

The cradle 22 can thus oscillate substantially horizontally andperpendicularly of the axis of rotation of the crankshaft; and excessivedeflection may be prevented by fixed abutmcnts (not shown). Theoscillation is free in the sense that the movements of the cradle arenot positively guided, and within the limits fixed by abutments, areopposed only by friction, inertia forces and gravity. Because the cradle22 is suspended in pendulum fashion by means of pendulum links 23, thecradle 22 is slightly raised as it is moved in one horizontal directionor the other from its mean position. The mean position is defined by thependulum links 23 being vertical and the cradle 22 and the crankshaft 14being in their lowermost position. Thus it can be seen that gravityalways tends to return the cradle 22 to its mean position. As shown inFIG. I, the cradle 22 also carries the motor 13 which is connected bymeans of a belt 13a to a pulley 14a which drives crankshaft 14. Themotor 13 thus is oscillated with the cradle 22.

As the sash I8 is reciprocated vertically in the main frame 11 duringthe sawing operation, cradle 22 and crankshaft 14 are oscillatedtransversely about their mean position on the pendulum links 23. Thistransverse oscillation is caused primarily by the counterweight (whichoffsets the center of gravity of the crankshaft from the axis ofrotation) and is of the same frequency as the vertical reciprocation ofthe sash 18 but has a phase shift relative to the latter such that theeradlc 22 and the crankshaft 14 are in their left-hand extreme position(see FIG. I and FIG. 3) when the downwardly moving sash is about halfwayto its lower extreme position. When the sash I8 is in its upper or lowerextreme position. the cradle 22 and the crankshaft l4 are in their meanposition, and when the upwardly moving sash 18 is about halfway to itsupper extreme position, the cradle and the crankshaft are in theirright-hand extreme position.

The amplitude of the transverse oscillation of the eradle 22 naturallydepends on the geometry, the masses of the cradle 22 and the crankshaftl4 and the other moving parts, but for practical purposes may beconsidered independent of the speed of rotation of the crankshaft. As anon-limitating example. the deflection has been found to be about fivecm in either horizontal direction from the mean position in a gang sawconstructed in accordance with the invention where the combined mass ofthe cradle 22, the crankshaft 14, the connecting rod and the sash 18 isabout 3,500 kilograms. In this example, the speed of rotation of thecrankshaft is approximately 380 rpm, the length of the pendulum links 23is approximately 24 cm and the transverse distance between the links 23,is approximately 150 cm.

In this gang saw, the combined tensile force in the pendulum links 23,i.e., the force imposed on the main frame 11 by the cradle 22,fluctuates between 7,300 and 8,400 pounds (32,300 and 37,400 Newtons).The vertical component of this force is almost exclusively the weight ofthe recited components. The horizontal force component fluctuatesbetween 0 and 1,500 pounds (0 and 7,350 Newtons) in either direction. Ifthe crankshaft 14 has been stationary in the main frame ll is the casein conventional gang saws, it has been found that the horizontal forcecomponent would have fluctuated between 0 and 31,000 pounds (0 and137,000 Newtons). It may be readily appreciated that the foregoingspecific embodiment results in a substantial reduction of the horizontalforce component.

From a consideration of FIG. 3 and FIG. 4, it can be seen that when thecrankshaft 14 is at its maximum positive or negative x coordinateposition, the sash is at its mean or zero origin position on the ycoordinate. Conversely, when the sash is displaced to its maximumpositive or negative y coordinate position, the crankshaft is displacedto its mean or zero origin x coordinate position. Noting FIG. 4 inparticular, there is shown the re lationship between the phase angle andthe displacements along the x and y coordinates.

In the illustrated embodiment, the transverse oscillation is opposedalmost exclusively by gravity. However, it would be within the scope ofthe invention to provide springs or other means constantly urging thecradle 22 towards its mean position. Naturally, the pendulum links 23need not be exactly parallel and vertical in the mean position as shownbut can be disposed such that they are slightly inclined to the verticalplane in the mean position.

Moreover. although in the illustrated embodiment the motor 13 is carriedby and oscillates with the cradle 22, the motor 13 may be stationaryrelative to the frame 11. In this case the relative movements of thecradle and the motor are accomodated by the power transmission betweenthe motor and the crankshaft.

The foregoing specific embodiment has been described for the purpose ofillustrating the principles of the present invention, and the same issubject to modification without departure therefrom. Therefore, theinvention includes all modifications encompassed within the spirit andscope of the appended claims.

What is claimed is:

1. In a gang saw having a frame and a driven crankshaft, means forsubstantially damping out vibrations transferred from the crankshaft tothe frame, said damping means comprising:

a. means for operatively journaling said crankshaft said meanscomprising a cradle,

b. means for movably securing said journaling means to said framewherein said movably securing means allows substantially horizontaldisplacement of said crankshaft with respect to said frame when saidcrankshaft has a force applied thereto and,

wherein said movably securing means comprises a plurality of links, eachof said links being pivotally connected to said cradle and pivotallyconnected to said frame,

wherein said links are disposed in substantially parallel relationshipto each other which enable said cradle to be displaced in asubstantially horizontal direction when a connecting rod imparts arotational movement to said crankshaft,

said connecting rod is operatively connected at a distal end from saidcrankshaft to one end of a series of substantially parallel saw blades,said distal end being operatively connected to one end of said sawblades by means of a first sash vertically displaceable within a firstvertical guide disposed in said frame, and

wherein said saw blades have their opposite end being operativelyconnected by means of a second sash vertically displaceable within asecond vertical guide disposed in said frame.

so that when said first sash and said second sash are said horizontalmean and extreme positions of said crankshaft resulting from apendulum-like movement of said cradle caused by forces applied to saidsaw blades and asid connecting rod from a wood sawing operation.

2. A gang saw comprising:

a. a frame,

b. a sash having a plurality of parallel vertical saw blades,

c drive means for reciprocating said sash up and down in said frame andincluding a crankshaft rotatable about an axis and a connecting rodinterconnecting said sash and said crankshaft.

d. means journaling said crankshaft. and

e. means movably securing said journaling means to said frame andallowing oscillation of said journaling means and said crankshaft withrespect to the frame independently of the reciprocation of the sash andin a substantially horizontal direction transverse to the axis ofrotation of said crankshaft.

3. A gang saw as recited in claim 2 wherein said journaling meanscomprises a cradle and wherein said securing means comprises a pluralityof links, each of said links being pivotally connected to said cradleand pivotally connected to said frame.

4. A gang saw as recited in claim 3 wherein said links are disposed insubstantially parallel relationship to each other and pivotallyconnected to said cradle on either side of said crankshaft.

1. In a gang saw having a frame and a driven crankshaft, means forsubstantially damping out vibrations transferred from the crankshaft tothe frame, said damping means comprising: a. means for operativelyjournaling said crankshaft, b. means for movably securing saidjournaling means to said frame wherein said movably securing meansallows substantially horizontal displacement of said crankshaft withrespect to said frame when said crankshaft has a force applied thereto,said journaling means comprises a cradle and wherein said movablysecuring means comprises a plurality of links, each of said links beingpivotally connected to said cradle and pivotally connected to saidframe, said links are disposed in substantially parallel relationship toeach other which enable said cradle to be displaced in a substantiallyhorizontal direction when a connecting rod imparts a rotational movementto said crankshaft, said connecting rod is operatively connected at adistal end from said crankshaft to one end of a series of substantiallyparallel saw blades, said distal end being operatively connected to oneend of said saw blades by means of a first sash vertically displaceablewithin a first vertical guide disposed in said frame, and wherein saidsaw blades have their opposite end being operatively connected by meansof a second sash vertically displaceable within a second vertical guidedisposed in said frame, so that when said first sash and said secondsash are vertically displaced to a mean vertical position, saidcrankshaft will be correspondingly displaced to a substantiallyhorizontal extreme position with respect to said frame, and when saidfirst sash and said second sash are displaced to their extreme verticalpositions, said crankshaft will be correspondingly positioned in ahorizontal mean position with respect to said frame, said horizontalmean and extreme positions of said crankshaft resulting from apendulum-like movement of said cradle caused by forces applied to saidsaw blades and asid connecting rod from a wood sawing operation.
 2. Agang saw comprising: a. a frame, b. a sash having a plurality ofparallel vertical saw blades, c. drive means for reciprocating said sashup and down in said frame and including a crankshaft rotatable about anaxis and a connecting rod interconnecting said sash and said crankshaft,D. means journaling said crankshaft, and e. means movably securing saidjournaling means to said frame and allowing oscillation of saidjournaling means and said crankshaft with respect to the frameindependently of the reciprocation of the sash and in a substantiallyhorizontal direction transverse to the axis of rotation of saidcrankshaft.
 3. A gang saw as recited in claim 2 wherein said journalingmeans comprises a cradle and wherein said securing means comprises aplurality of links, each of said links being pivotally connected to saidcradle and pivotally connected to said frame.
 4. A gang saw as recitedin claim 3 wherein said links are disposed in substantially parallelrelationship to each other and pivotally connected to said cradle oneither side of said crankshaft.